A number of underwater support structures exist that need to be inspected for potential damage. One example of an underwater support structure is for an offshore platform such as an oil drilling platform. Underwater support structures of offshore platforms are often made of welded tubular members, some of which are normally water filled and some of which are normally air filled. Whether air filled or not, the tubular members have marine growth on them, making it difficult to visually inspect the tubular members for damage and cracks. When an offshore platform is stressed, for example in a hurricane, underwater inspections of the structural members must be performed. If a crack develops on an air filled member, it will flood. Identifying the flooded members during an inspection is one way of finding the cracks.
Previous methods at identifying flooded members have included the use of acoustic devices which are placed in contact with the members being inspected. One example of an acoustic device is an ultrasonic probe which when brought in contact against a structural member is set to ignore the first couple of inches, then listens for reflections from the possible steel to air or water, water to air or air to water, and water or air to steel interfaces over a pre-set range. Another inspection device that is used is a radiographic (i.e. x-ray) device which does not need to be in contact with the member, but does require close proximity, to inspect the member in a submerged environment, not to mention the difficulties with deploying X-ray underwater.